FR3024906B1 - DEVICE FOR MEASURING AN ELECTROMAGNETIC FIELD BASED ON METAMATERIAL - Google Patents

Abstract

An electromagnetic field measuring device uses metamaterials to manipulate electromagnetic fields. Such a device is useful in a number of applications including for example the gradiometric staking of downhole.

Description

Electromagnetic Field Measuring Device Based on METAMATERIAL

DOMAIN OF DESCRIPTION

The present disclosure generally relates to electromagnetic field measuring devices and more specifically to an electromagnetic field measuring device which divides and reverses electromagnetic waves by the use of metamaterials.

CONTEXT

Determining the position and direction of a conductive pipe (metal housing, for example) accurately and efficiently is required in a number of downhole applications. The most important of these applications may be the case of a blown well in which the target well must precisely join a relief well in order to interrupt the blast of the explosion. Other important applications include the drilling of a well parallel to an existing well in steam induced gravity drainage ("SAGD") systems, which avoid collisions with other wells in a dense oilfield where the wells are drilled close to one another and the monitoring of a subterranean borehole using a metal pipe injected on the ground as a reference.

The classical approaches have tried to provide solutions to this problem. In one method, an electrode source is used to induce current on the target housing to produce a magnetic field. The gradient of the magnetic field radiated by the target housing, in addition to the magnetic field itself, is measured by means of two receivers which often require a calibration in the field. Thanks to a relationship between the magnetic field and its gradient, a precise staking measurement is carried out. However, since two receivers are used, field calibration of the receivers is often required.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1A shows a radius R along an initial space having an x-y axis.

Fig. 1B shows a radius R along a transformed space having an u-v axis.

Figure IC shows a transformed space for a masking application.

Figure ID shows a number of R-rays in a 3D masking.

FIG. 2 represents an invisibility mask operating at 8.5 GHz, realized using split ring resonators as metamaterials, according to an exemplary embodiment of the present description.

FIG. 3 represents an electromagnetic measuring device according to an exemplary embodiment of the present description.

FIG. 4A is an exploded view of the electromagnetic measuring device of FIG.

FIG. 4B represents the non-inversion of rotation supports of the electromagnetic field.

FIG. 4C represents rotational supports of the inverted electromagnetic field.

FIG. 4D is a flowchart representation of the electromagnetic field measuring device of FIG. 3 having two electromagnetic field rotation supports.

FIG. 5 is a flowchart representation of an electromagnetic field measuring device having a single electromagnetic field rotation support, according to another embodiment of the present disclosure.

Figure 6 finally shows the electromagnetic measuring devices deployed in a drilling and drilling cable application, according to some illustrative methods of the present description.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Illustrative embodiments and related methodologies of the present disclosure are described below as may be employed in an electromagnetic field measuring device which reverses and divides electromagnetic waves. For the sake of clarity, not all features of an actual facility or methodology are mentioned in this description. It will be appreciated, of course, that in developing any such embodiment, many specific implementation decisions must be made to achieve the specific objectives of the developers, such as compliance with system-related constraints and related issues. commercial activity, which must vary from one installation to another. It will also be noted that this development effort can be complex and time-consuming, but can be a routine undertaking for specialists benefiting from this description. Other aspects and advantages of the various embodiments and related methodologies of the description should appear after consulting the description of the following drawings.

In this context, methodologies and illustrative embodiments of the present disclosure describe electromagnetic field measuring devices that manipulate electromagnetic waves or electromagnetic fields using transform optics to thereby produce signals susceptible to be used for a number of applications. In a generalized illustrative embodiment, a metamaterial-based measurement device comprises a receiver having a first and a second input through which electromagnetic waves can be received. An electromagnetic field rotation support ("EMF") consisting of a metamaterial is coupled to the second input channel of the receiver. The EMF rotation support receives an electromagnetic field at a first spatial angle, and then rotates the first spatial angle to a second spatial angle. The rotated electromagnetic field is therefore spatially out of phase with the initial electromagnetic field of a given degree. In other words, the spatial phase shift of a given degree means that one component of the electric / magnetic field represents a rotated version of the other after a rotation of a certain angle is applied by the metamaterial of the rotational support of the EMF.

In operation of this generalized embodiment, the receiver receives electromagnetic fields in its first and second input channels. The electromagnetic field received through the first input channel may be an electromagnetic field directly from the environment, while the electromagnetic field received through the second input channel is the rotated electromagnetic field. After reception, the receiver superimposes the two electromagnetic fields to produce a signal that can be further processed for any desired application. The signal may for example be used to obtain a gradiometric measurement. In these embodiments, the turned electromagnetic field rotates substantially 180 ° with respect to the initial electromagnetic field, which substantially reverses the two fields, as will be described in more detail below. In another embodiment, two EMF rotation supports may be coupled to the receiver to provide two electromagnetic fields that have been rotated substantially 90 ° in the opposite direction to each other, resulting in also inverted electromagnetic fields that are received at the receiver.

Accordingly, the embodiments described herein are particularly useful for gradiometric applications because only one receiver is required to perform a gradient measurement. Moreover, as only one receiver in these applications is needed, no need for field calibration is needed. These and other advantages and applications of the present description will become apparent to the specialists benefiting from this description.

As already mentioned, the illustrative embodiments of the present description use transformation optics to regulate electromagnetic fields. These transformations can be carried out in a number of ways including for example metamaterials. Metamaterials are artificially engineered composites that inherit their electrical properties from the geometry and configuration of their constituent unit cells. Metamaterials can be obtained in many different ways depending on the operating frequency. Of the illustrative embodiments described herein, the metamaterial based electromagnetic field measuring device is designed for inverted division electromagnetic waves.

We must first describe some principles of the optics of transformation. Fig. 1A shows a radius R along an initial space 2 having an x-y coordinate system. Suppose that the underlying grid (initial space 2) is "elastic" and can be deformed to achieve some form of field as shown in Figure 1B. As a result, a 2T transformed space is formed in a u-v coordinate system. As a consequence of the shape invariance of the Maxwell equation in coordinate transformation, these transformations can be interpreted as if the initial medium in the deformed space was replaced by a globally anisotropic and inhomogeneous medium. Materials with these properties may not exist in nature and therefore they are called "metamaterials." An illustrative application of transform optics is invisibility masking. Figure IC shows a transformed space 2T for a masking application. Here, the space 2T is transformed to create an enclosure in the inner region (p <R]), while keeping the gate intact in the outer region (p> R2). The region Ri <p <R2 is that where a metamaterial is used to mimic the grid deformation represented. The represented transformation makes it possible to delicately direct the rays around the internal region regardless of the material content of this internal space, which makes any object placed in the internal space invisible, as shown in FIG.

We will now give a mathematical description of the transformation optics. In the initial space (Fig. IA), we have Maxwell's equations:? XE = ~> | tH eq (la) and V x H = JuieE -t- J, eq (1b).

Consider the following transformation in the cylindrical coordinates: p = p (ρ, φ, ζ ') eq (2a), φ * = φ' (ρ, φ, ζ) eq (2b), and s * - ζ'ίρ, φ. 2) eq (2c).

Maxwell's equations are invariant in coordinate transformation. In the transformed space, they take the following form; V 'x E' = eq (3a) and + eq (3b), where:. _ ΑμΑτ lAl eq (4a),

. _ AeAT lAl éq (4b), I -, s ΙΑ ,, Ι éq (4c) and 'dp ρδφ dz A _ ρ'δφ' ρ'δφ 'ρ'δφ' dp ρδφ dz dz dz 'dp ρδφ dz eq (5) constitute the Jacobian matrix of the transformation. The properties of the materials and the equivalent current source are to be used above to achieve the prescribed coordinate transformation. Transformations that preserve grid continuity across the transformed space boundary produce non-reflective, iso-impedance metamaterials. Another class of transformations exists, called embedded transformations, in which gate continuity is broken and therefore non-reflective transmission through the interface of the metamaterial / background medium is not guaranteed. Incoφorated transformations, however, provide a greater degree of flexibility in manipulating fields outside the metamaterial device, and can be designed to limit spurious reflections.

The practical embodiment of metamaterials used in some exemplary embodiments of the present description will now be described. While classical materials achieve their macroscopic properties from the chemical composition of the constituent atoms, metamaterials reach their macroscopic properties from artificially elaborated unit cells. Metamaterials have been made in many different ways depending on the application and frequency of operation. Some illustrative achievements will now be described; however, these achievements are neither exhaustive nor intended to limit the scope of this description,

FIG. 2 represents an invisibility mask operating for example at 8.5 GHz and realized using split ring resonators as metamaterials, which can be used as metamaterial in the illustrative embodiment of the invention. this description. The two-dimensional invisibility mask illustrated 4 requires the radial component of the permeability tensor (// ") to vary radially, as shown by the inserts 6 of FIG. 2, one of them being approximately 30 mm and the other at about 60 mm. This profile is achieved using ten cylinders 8 with printed split ring resonators ("SRRs") 10. The dimensions of the SRRs 10 in each cylinder are adjusted to obtain the required profile. In order to be able to describe the SRR series with effective macroscopic material properties, the size of the unit cell must be significantly smaller than the operating wavelength, which is called the homogenization condition. Nevertheless, the size of the SRRs 10 must be large enough to resonate at or near the operating frequency.

In other embodiments, the metamaterials used may be other electrical and magnetic layers of metamaterials. In these embodiments, the electrical layers realize the discretized profile λ &amp; thanks to the five sets of electric resonators LC ('ELC'), while the magnetic layers achieve the discretized Ayy Ayy profile thanks to the SRR. The Negative Refractive Index ('NIR') lens (also known as the perfect lens) is another example of a built-in optics of transformation where double negative metamaterials ('DNG') are used. also left-handed metamaterials (LH) Negative permeability is achieved using SRRs, while negative penittiveness is achieved using fine wires.

At lower frequencies, the dimensions of the SRRs and ELCs must resonate while the operating frequency becomes too large for practical realization. However, localized components can be used to achieve resonance at lower frequencies without increasing the cell dimensions of the units. For example, single negative ('SNG') lenses useful in magnetic resonance imaging ('MRI') can be used as a metamaterial. These charged capacitance lenses were used to improve the sensitivity and spatial resolution of RF coils in MR systems. It will be noted that since the operating wavelength of the MRI RF coils is much greater than the dimensions of the coil (quasi-magnetostatic regime), a NIR lens MM may suffice as a SNG lens with μ, r = -1.

According to still other illustrative embodiments, another design of DNG metamaterials that can be used are chiral materials. A chiral metamaterial consists of insulated metal strips wound in a helix, and then the individual helices are stacked in a 3D array to form an isotropic DNG structure. This design has the advantage that its unit cells (chiral helices) can have internal resonances with dimensions of the order of 1 / 1000th of the operating wavelength. This characteristic is particularly important for designing metamaterials operating at very low frequencies (quasi-static metamaterials).

A feature of the metamaterial fabrication techniques previously described is that it rests on resonant structures, in one way or another. Thus, the metamaterial is highly dispersive and subject to loss when it operates near resonance, which also means that a metamaterial with given properties can only be designed to operate at a single frequency.

There are a number of other embodiments of metamaterials that can be employed in embodiments according to the present description. The use of metamaterials has also been extended, for example, to quasi-static and DC applications. Examples include a DC diamagnetic metamaterial, a DC magnetic mask, and an electric DC concentrator.

After describing a number of metamaterial embodiments, illustrative embodiments of the present description will now be described. Although the electromagnetic field measuring devices described herein may be used in a number of applications, the following description should focus on wellbore classification applications to accurately and reliably position a well being drilled. , the "injector" well, relative to a near-target first well, usually the producing well, so that the injector can be kept approximately parallel to the producing well. In such an embodiment, the target well must have a higher conductivity than the surrounding formation, which can be achieved by using an elongated conductive body along the target well, such as casing which is already present in most wells to maintain well integrity. The specialists benefiting from this description will include these applications and / or adaptations as well as others.

FIG. 3 represents an electromagnetic measuring device 300 placed along a wellbore, according to an illustrative embodiment of the present description. In this embodiment, a first well 20 is drilled using any suitable drilling technique. Then this first well 20 receives the casing 22. A second well 24 is then drilled using a suitable drilling set (not shown) which may for example be a well logging assembly ('LWD'). a measuring assembly being drilled ('MWDj or other desired set of wells.) Although a second well 24 is described as being subsequently drilled, according to other embodiments, the first well 20 and the second well 24 can be drilled simultaneously, in which case the drill collar of the first well 20 can act functionally as casing 22.

After drilling the second well 24 (ie, the classification borehole), a downhole cable is deployed through the drill bit 26 to perform staking operations. Staking operations can be used to measure the distance and direction of one well from the other that can be used in applications to drill parallel wells during an SAGD operation, to avoid collisions of wells in congested areas or intersections between wells in relief well operations. The electromagnetic measuring device 300 forms a pailie of the assembly forming a drilling cable, and it is housed in a housing 28. The housing 28 can be at any temperature and under any pressure resistant to the housing suitable for downhole staking applications. It may for example be a rod-type section which is made of a non-ferrous metal, such as stainless steel. As indicated below, the electromagnetic measuring device 300 allows, for example, a gradiometric staking by means of a single receiver.

FIG. 4A is an exploded view of the electromagnetic measuring device 300. As can be seen, the electromagnetic measuring device 300 comprises a receiver 30 located between two rotational supports of the EMF 32a and 32b. The receiver 30 and the EMF rotation supports 32a and 32b do not need to contact each other, but the distance between the receiver 30 and the EMF rotation supports 32a and 32b must be limited to reduce geometric diffusion or propagation effects. The receiver 30 may for example be formed of coils, solenoids, magnetometers or a number of other embodiments that are equivalent to magnetic or electric dipoles. The rotational supports of the EMF 32a and 32b consist of a metamaterial, as already described, which both act as electromagnetic field polarization rotators. The rotational supports of the EMF 32a and 32b are two symmetrical halves of the same metamaterial with respect to the measuring center of the receiver 30. In some embodiments, the rotational supports of the EMF 32a and 32b may be separate pieces. coupled to both sides of the receiver 30. In other embodiments, the EMF rotation supports 32a and 32b form a monolithic piece having a spacing (e.g., a groove) extending through its center, where the receiver 30 can be positioned. Be that as it may, in all embodiments, the EMF rotation devices located on either side of the receiver 30 must be symmetrical with respect to the measuring center of the receiver 30.

The rotational supports of the EMF 32a and 32b can be mutually reversed. Figs. 4B and 4C illustrate this concept, Fig. 4B showing non-inverted EMF rotation supports and Fig. 4C showing inverted EMF rotation supports. In Figure 4B, EMF rotation supports A and B are non-inverted, which means that for the same given incident field, they produce the same field vector direction at their receiver ports. In FIG. 4C, however, the EMF rotation supports A and B have been inverted, which means that for the same given incident field, they produce the opposite field vector direction at their receiver ports. In this illustrative embodiment, the identical EMF rotation supports A and B are rotated 90 ° relative to each other so as to produce electromagnetic signals out of phase with the receiver 30. Here, the "phase Corresponds to the spatial phase angle of the electromagnetic wave, which is the degree of rotation of the wave in space. Thus, the phase shift corresponds to a misalignment (here called the "spatial phase shift"). The phase shift of a number of degrees of a component of the electric / magnetic field corresponds to a rotated version of the other after application of the rotation of a certain angle by the rotational supports of the EMF.

Fig. 4D is a flowchart representation of the electromagnetic field measuring device 300 useful for illustrating the rotation of the spatial phase angle. As already mentioned, the rotational supports of the EMF 32a and 32b have been rotated 90 ° relative to each other. Thus, during operation, an electromagnetic wave 34 is emitted from a source such as for example a tube well or the environment itself. As indicated by the arrows 34, the electromagnetic waves have a first spatial angle in the same direction as their path in the inputs 36 of the rotational supports of the EMF 32a and 32b. Due to the inverted nature of the EMF rotation supports 32a and 32b, the metamaterial of the EMF rotation support 32a rotates from the first spatial wave angle 34 by 90 ° to a second spatial angle. which produces a rotated electromagnetic wave 34R at the output 38. The metamaterial of the EMF rotation support 32b rotates from the first spatial angle of its wave 34 by 90 ° also to a second spatial angle. Due to the inverted nature of the rotation suppoxt of the EMF 32b however, this rotation takes place in a direction opposite to the direction of rotation of the electromagnetic wave 34R. Thus, the rotational support of the EMF 32b produces a rotated electromagnetic wave 34R 'at its output 38. The inputs 36 represent the incident magnetic fields (eg EM wave 34) requiring measurements. The outputs 38 represent the magnetic fields (EM wave 34R, 34R ') which are electromagnetically superimposed on the receiver to create the gradient signal.

Referring again to FIG. 4D, it can be seen that the receiver 30 contains a first input channel 40 and a second input channel 42 through which it receives the electromagnetic waves. The rotated electromagnetic wave 34R is received through its first input channel 40, whereby a first signal is generated. The rotated electromagnetic wave 34R 'is received through the second input channel 42, whereby a second signal is produced. Since the second spatial angles of the rotated electromagnetic waves 34R and 34R 'are oriented in the opposite direction of a total of 180 ° in this example, the first and second signals obtained can be used to determine the gradient. In this illustrative embodiment therefore, the first and second signals are electromagnetically superimposed on the receiver 30 to produce a signal proportional to a gradiometric measurement of the electromagnetic wave 34. When a geometric diffusion likely to occur between the rotation supports 32a and 32b and 30 is ignored, the measurement is equivalent to the difference between the magnetic fields at the inputs 36 with a spacing equivalent to the distance between the inputs 36. However, when the geometric scattering effect is included, the equivalent spacing may differ from the ideal value. Thus, up to a scaling constant, the reading of the receiver 30 is proportional to the gradient of the ambient field. The scaling constant can be calculated through a calibration procedure involving laboratory measurements with a controlled reference source.

Therefore, because of the inverted nature of the metamaterial, the illustrative embodiment of the electromagnetic field measuring device 300 allows the calculation of the gradient through a single measurement (through a single receiver). In contrast, the prior art gradient tools (eg, staking tools) require the use of two sensitive receivers to measure electromagnetic fields to obtain the gradient. The processing circuits then analyze the measured fields, whereby they are differentiated and divided by their spacing to obtain the gradient. In the illustrative embodiments described herein, however, the metamaterial of the EMF rotation supports performs the gradient calculations and therefore it is not necessary for the processing circuits to perform these calculations. Moreover, since only one receiver can be used, it is not necessary to use multiple receiver calibrations as with the prior art tools.

Fig. 5 is a flowchart representation of an electromagnetic field measuring device 500 for illustrating the rotation of the spatial phase angle, according to at least one embodiment of the present disclosure. The electromagnetic field measuring device 500 is somewhat similar to the device 300 already described and can therefore be best understood with reference to it, where like numbers indicate like elements. Unlike the system 300 however, the electromagnetic field measuring device 500 uses only one rotation support of the EMF 44. The metamaterial used in the rotation support of the EMF 44 is designed to rotate the spatial angle of an incident electromagnetic wave of 180 °. As already indicated, this is achieved by using a metamaterial that performs a coordinate transformation equivalent to a rotation of 180 °. This metamaterial can be made using a chiral material or another type of suitable material.

In operation of the electromagnetic field measuring device 500, therefore, an electromagnetic wave 34 is emitted from a source such as a cased wellbore or the environment itself. As indicated by the arrows 34, the electromagnetic waves have a first spatial angle oriented in the same direction as they travel through the inlet 36 of the rotation support of the EMF 44. Simultaneously, the electromagnetic wave 34 also traverses the first input channel 40 of the receiver 30 to give a first signal. The metamaterial of the EMF rotation support 44 rotates from the first spatial angle of wave 34 180 ° to a second spatial angle, which produces a rotated electromagnetic wave 34R at the output 38. The rotated electromagnetic wave 34R is received through the second input channel 42 whereby a second signal is generated. Since the second spatial angle of the rotated electromagnetic wave 34R is oriented 180 ° out of phase with electromagnetic wave 34, the first and second signals obtained can be used to determine the gradient. In this exemplary embodiment therefore, the receiver 30 then superimposes the first and second signals to produce a signal proportional to a gradiometric measurement of electromagnetic wave 34.

As already indicated, the electromagnetic field measuring devices can be used in different applications. Such applications include, for example, EM-controlled source study measurements, well or well-bottom tomography applications such as logging or drilling cables. Although Figure 3 shows an electromagnetic field measuring device 300 placed along a drill string, the following example will describe its use along a drill assembly. With reference to FIG. 3 therefore, when used in a downhole staking application, a drill string (comprising an electromagnetic field measuring device 300, 500) (not shown) may be deployed down the well to drill a first well 24 (eg, the injection well) after or during the drilling of the second well (eg, the producing well). To maintain the first well 24 at the desired distance and direction of the second well, a current / is induced along the casing 22 of the second well 20 which generates a magnetic field 34 radiating from the tubing 22 to the electromagnetic field measuring device 300, 500 in the first well 24. The electromagnetic fields 34 are then received by the electromagnetic field measuring device 300, 500, whereby the gradient is determined as already indicated. Then the gradiometric data can be used to determine the distance and direction to the second well 20. Once the relative position is determined, processing circuits can then produce the necessary signals to direct the drill string in the direction necessary for maintain the desired distance and direction from the second well 20.

Figure 6 illustrates a system 600 for staking operations according to an illustrative embodiment of the present description. Note that the system 600 may also contain a pumping system or other operations. The system 600 contains a drilling rig 602 located at a surface 604 of a wellbore. The drilling rig 602 provides support for a downhole apparatus, including a drill string 608. The drill string 608 enters a rotary table 610 to drill a well bore / well bore 612 through the underground formations 614. The drill string 608 contains a Kelly 616 (in its upper part), a drill pipe 618 and a bottom hole assembly 620 (located at the bottom of the drill pipe 618). . In some illustrative embodiments, the downhole assembly 620 may contain drill collars 622, a downhole tool 624 and a drill bit 626. Although the downhole tool 624 may be any tool among a number of different types including measuring tools during drilling ('MWD'), staking during drilling ('LWD'), etc. ; in this embodiment, the downhole tool 624 is any of the electromagnetic field measuring devices described herein.

During drilling operations, the drill string 608 (comprising a Kelly 616, a drill pipe 618 and a downhole assembly 620) can be rotated by a rotary table 610. In addition to or in place of this rotation, the downhole assembly 620 can also be rotated by a motor which is at the bottom of the well. The drill collars 622 can be used to add weight to the drill bit 626. The drill collars 622 also optionally stiffen the downhole assembly 620 by allowing it to transfer the weight to drill bit 626. The weight provided by the weights Also, 622 helps bit 626 to enter surface 604 and subterranean formations 614.

During drilling operations, a slurry pump 632 may pump drilling fluid (eg, drilling mud) from a sludge pit 634 through a pipe 636 to the drill pipe 618. then to drill bit 626. Drilling fluid may flow out of drill bit 626 and return to the surface through an annular zone 640 between drill pipe 618 and the sides of drill hole 612. Drilling fluid may then be returned to the mud pit 634, for example through the pipe 637, then the filter is filtered. The drilling fluid cools bit 626 and allows bit 626 to be lubricated during the drilling operation. In addition, the drilling fluid suppresses cuts in the underground formations 614 produced by bit 626.

Referring again to FIG. 6, it can be seen that the downhole tool 624 also includes any number of sensors that follow different downhole parameters and that produce data that is recorded in at least one different recording medium in the downhole tool 624. Otherwise, the data can be transmitted to a remote site (eg on the surface) and processed accordingly. These parameters may include staking data related to the various characteristics of the subsurface formations (such as resistivity, radiation, density, porosity, etc.) and / or well hole characteristics (eg size, form, etc.), etc.

Figure 6 also illustrates another embodiment in which a rig system is deployed. In such an embodiment, the drill string system may contain a downhole tool body 671 coupled to a base 676 by a staking cable 674. The staking cable 674 may contain, but not be limited to, a electrical cable (multiple power and telecommunication cables), single cable (single conductor) and cable (not for power supply or telecommunications). The base 676 is above the ground and optionally includes support devices, telecommunication devices and computing devices. Tool body 671 houses any of the electromagnetic field measuring devices 672 described herein. In one embodiment, a power supply (not shown) is in tool body 671 for conducting power to tool 671. During operation, a rigging cable system is usually sent at the bottom of the hole after completion of part of the drilling. More specifically, according to some embodiments, the drill string 508 creates a wellbore 612, then the drill string 608 is removed, and the drill string system is introduced into the wellbore 612, as a specialist benefiting from this description will understand it. It should be noted that only one wellbore is shown for the sake of simplicity, in order to show the tools deployed in drilling and cable applications. In some applications, such as staking, multiple drill holes will be drilled as known in the art.

Metamaterials have many advantages when applied in downhole applications. First, the narrow band, single-frequency operation of many downhole tools works well with a metamaterial because practical metamaterial implementations work well on narrow strips. Second, the cylindrical geometry of many downhole tools also provides an advantage. Here, some possible practical metamaterial implementations have two dimensional variations without variations in the third dimension. In boreholes, a geometric variation in the axial dimension can often be neglected, which gives a good match.

Third, the low frequency operating range of many downhole tools makes the homogenization principle easily applicable. The polarization-rotating metamaterials are based on the incorporated transformation optics, which means that the gate continuity across the metamaterial interface is broken. This gives rise to false distortion when the electromagnetic signal passes through this interface. In practice, however, this distortion has been neglected, suilout low operating frequencies implemented in the staking.

Fourth, electric and magnetic fields are decoupled in many downhole tools, making it easier to make metamaterials using a reduced set of material properties. Fifth, most downhole tools have a predefined field bias, which makes it easier to design the metamaterial from a smaller set of parameters. Sixth, if SNG and DNG are optional, one can design low-loss, non-resonant metamaterials operating at much longer wavelengths than the unit cell.

As a result, the electromagnetic field measuring devices described here allow differential gradient staking measurements using a single installed receiver instead of two as in conventional tools - which reduces the cost of the tool. The reverse split metamaterial can be produced in the factory to ensure symmetry and therefore no further calibration is required in the field. Moreover, since only one receiver is used, no calibration of the multiple receivers is necessary either.

The embodiments described herein further relate to any of the following: 1. An electromagnetic field measuring device comprising a receiver comprising: a first input channel through which it receives an electromagnetic field thereby producing a first signal thanks to the receiver; and a second input path through which it receives an electromagnetic field thereby producing a second signal through the receiver; and a first electromagnetic field (EMF) rotation support coupled to the second input channel of the receiver, the first EMF rotation support comprising: an input for receiving an electromagnetic field having a first spatial angle, the medium rotating the EMF being adapted to rotate the first spatial angle to a second spatial angle; and an output through which the electromagnetic field having the second spatial angle passes into the second input channel of the receiver to thereby produce the second signal. 2. Device according to paragraph 1, wherein the first rotational support of the EMF consists of a metamaterial. 3. Device according to paragraph 1 or 2, wherein the receiver is a magnetic dipole. 4. Device according to any one of paragraphs 1 to 3, wherein the receiver is an electric dipole. An apparatus according to any one of paragraphs 1 to 4, wherein the EMF rotation support is adapted to rotate the first spatial angle to a second spatial angle which is substantially 180 ° out of phase. spatial with respect to the first spatial angle; and wherein the receiver is adapted to superimpose on the first and second signals to thereby produce a signal proportional to a graded measurement. Apparatus according to any one of paragraphs 1 to 5, further comprising a second EMF rotation support coupled to the first input channel of the receiver, the second EMF rotation support comprising: an input for receiving an electromagnetic field having a first spatial angle, the second rotation support of the EMF being adapted to rotate the first spatial angle to a second spatial angle; and an output through which the electromagnetic field having the second spatial angle reaches the first input channel of the receiver to thereby produce the first signal. 7. Device according to any one of paragraphs 1 to 6, wherein the first and second rotation supports comprise a substantially symmetrical construction with respect to a center of measurement of the receiver. Apparatus according to any one of paragraphs 1 to 7, wherein the second spatial angle produced by the first rotation support of the EMF is a rotation of substantially 90 ° with respect to the first spatial angle; the second spatial angle produced by the rotational support of the EMF is a rotation of substantially 90 ° with respect to the first spatial angle, the rotation of the second rotation support of the EMF being in opposite directions with respect to the rotation of the first rotation support of the EMF; and the receiver being arranged to superimpose the first and second signals to thereby produce a signal proportional to a gradiometric measurement. 9. Device according to any one of paragraphs 1 to 8, wherein the receiver is in a well hole; and where a source of the electromagnetic signals is in a second well. Apparatus according to any one of paragraphs 1 to 9, further comprising processing circuits for calculating a distance between the first and second wells through the first and second signals. 11. Device according to any one of paragraphs 1 to 10, wherein the receiver forms part of a cable or a drilling assembly. A method of performing an electromagnetic field measurement, which method comprises: receiving an electromagnetic field through a first input channel of a receiver and producing a first signal in the receiver; receiving an electromagnetic field in a first electromagnetic field rotation support ('EMF') coupled to the receiver; using the first rotation support of the EMF, rotating a first spatial angle of the electromagnetic field to a second spatial angle; and receiving the electromagnetic field having the second spatial angle in a second input channel of the receiver, and producing a second signal in the receiver. A method according to paragraph 12, further comprising calculating a gradiometric measurement from the first and second signals. A method according to 12 or 13, wherein rotating the first spatial angle of the electromagnetic field to the second spatial angle comprises rotating the first spatial angle of substantially 180 °. A method according to any one of paragraphs 12 to 14, wherein receiving the electromagnetic field through the first input channel of the receiver comprises receiving the electromagnetic field directly from an environment adjacent to the receiver. A method according to any of paragraphs 12 to 15, wherein receiving the electromagnetic field through the first input channel of the receiver comprises: receiving an electromagnetic field in a second EMF rotation support. coupled to the receiver; using the second rotation support of the EMF, rotating a first spatial angle of the electromagnetic field to a second spatial angle; and receiving the electromagnetic field having the second spatial angle in the first input channel of the receiver, and subsequently producing the first signal in the receiver. A method according to any one of paragraphs 12 to 16, wherein: by the first rotation support of the EMF, the rotation of the first spatial angle to the second spatial angle comprises the rotation of the first spatial angle of substantially 90 ° and thanks to the second rotation support of the EMF, the rotation of the first spatial angle to the second spatial angle comprises the rotation of the first spatial angle of substantially 90 ° in a direction opposite to the rotation applied by the first rotation support of GLT. The method of any one of paragraphs 12 to 17, wherein: a source of the electromagnetic fields is a first wellbore; the receiver is deployed along a second wellbore; and the method further comprises using the first and second signals to determine a distance between the first and second wellbore. The method of any one of paragraphs 12 to 18, further comprising deploying the receiver along a downhole assembly.

In addition, the methodologies described herein may be implemented in a system comprising processing circuits for implementing any of the methods, or in a computer program product comprising instructions that when executed at using at least one processor, causes the processor to perform any of the methods described herein.

Although various embodiments and methodologies have been presented and described, the description is not limited to these embodiments and methodologies and will be understood to include all modifications and variations, as will be apparent to one skilled in the art. It will therefore be understood that the description is not intended to be limited to the particular forms described. In fact, the intention is to cover all modifications, equivalents and alternatives forming part of the spirit and scope of the description as defined by the appended claims.

Claims (19)

An electromagnetic field measuring device comprising: a receiver comprising: a first input channel through which it receives an electromagnetic field and thereby producing a first signal by the receiver; and a second input path through which it receives an electromagnetic field thereby producing a second signal through the receiver; and a first electromagnetic field rotation support ('EMF') coupled to the second input channel of the receiver, the first EMF rotation support comprising: an input for receiving an electromagnetic field having a first spatial angle, the rotation support of the EMF being adapted to rotate the first spatial angle to a second spatial angle; and an output through which the electromagnetic field having the second spatial angle passes into the second input channel of the receiver to thereby produce the second signal. 2. Device according to claim 1, wherein the first rotation support of the EMF consists of a metamaterial. 3. Device according to claim 1 or 2, wherein the receiver is a magnetic dipole. 4. Device according to claim 1 or 2, wherein the receiver is an electric dipole. The device of claim 1 or 2, wherein: the EMF rotation support is adapted to rotate the first spatial angle to a second spatial angle that is substantially 180 ° out of the spatial phase relative to at the first spatial angle; and wherein the receiver is adapted to superimpose on the first and second signals to thereby produce a signal proportional to a graded measurement. The device of claim 1 or 2, further comprising a second EMF rotation support coupled to the first input channel of the receiver, the second EMF rotation support comprising: an input for receiving a an electromagnetic field having a first spatial angle, the second rotation support of the EMF being adapted to rotate the first spatial angle to a second spatial angle; and an output through which the electromagnetic field having the second spatial angle reaches the first input channel of the receiver to thereby produce the first signal. 7. Device according to claim 6, wherein the first and second rotation supports comprise a substantially symmetrical construction with respect to a measuring center of the receiver. The device of claim 6, wherein: the second spatial angle produced by the first rotation support of the EMF is a rotation of substantially 90 ° with respect to the first spatial angle; the second spatial angle produced by the rotational support of the EMF is a rotation of substantially 90 ° with respect to the first spatial angle, the rotation of the second rotation support of the EMF being in opposite directions with respect to the rotation of the first rotation support of the EMF; and the receiver being arranged to superimpose the first and second signals to thereby produce a signal proportional to a gradiometric measurement. 9. Device according to claim 1 or 2, wherein: the receiver is in a well hole; and where a source of the electromagnetic signals is in a second well. The apparatus of claim 9, further comprising processing circuitry for calculating a distance between the first and second wells by the first and second signals. 11. Device according to claim 9, wherein the receiver forms part of a cable or a drilling assembly. A method of performing an electromagnetic field measurement, which method comprises: receiving an electromagnetic field through a first input channel of a receiver and producing a first signal in the receiver; receiving an electromagnetic field in a first electromagnetic field rotation support ('EMF') coupled to the receiver; Using the first rotation support of the EMF, rotating a first spatial angle of the electromagnetic field to a second spatial angle; and receiving the electromagnetic field having the second spatial angle in a second input channel of the receiver, and producing a second signal in the receiver. The method of claim 12, further comprising calculating a gradiometric measurement from the first and second signals. The method of claim 13, wherein rotating the first spatial angle of the electromagnetic field to the second spatial angle comprises rotating the first spatial angle of substantially 180 °. The method of any one of claims 12 to 14, wherein receiving the electromagnetic field through the first input channel of the receiver comprises receiving the electromagnetic field directly from an environment adjacent to the receiver. The method of claim 12 or 13, wherein receiving the electromagnetic field through the first input channel of the receiver comprises: receiving an electromagnetic field in a second rotation support of the EMF coupled to the receiver; using the second rotation support of the EMF, rotating a first spatial angle of the electromagnetic field to a second spatial angle; and receiving the electromagnetic field having the second spatial angle in the first input channel of the receiver, and subsequently producing the first signal in the receiver. The method of claim 16, wherein: by the first rotation support of the EMF, the rotation of the first spatial angle to the second spatial angle comprises rotating the first spatial angle of substantially 90 °; and thanks to the second rotation support of the EMF, the rotation of the first spatial angle to the second spatial angle comprises the rotation of the first spatial angle of substantially 90 ° in a direction opposite to the rotation applied by the first rotation support of GLT. The method of any one of claims 12 to 14, wherein: a source of the electromagnetic fields is a first wellbore; the receiver is deployed along a second wellbore; and the method further comprises using the first and second signals to determine a distance between the first and second wellbore. The method of any one of claims 12 to 14, further comprising deploying the receiver along a downhole assembly.